<?php

echo $hello = '123';// Ok
echo $helloWorld = ' 456';// Ok
echo $hello_world = ' 789';// Ok
echo $hello_world23 = ' 888';// Ok


echo $hellWORLD = ' 0123';// OK :(
echo $_hello_world = ' 456';// OK :(


//echo $23hello = ' 456';// FAIL :(

echo "\n\n";
